Question 13
To stick one sheet of paper on the whiteboard, Anna must use four magnets to fix its four corners. To stick two sheets on the whiteboard, she needs only six magnets, as shown. To stick 32 sheets on the board, at least how many magnets does she need?
Clarification for the source-intended scored version: the sheets are placed edge to edge, in the same orientation, without overlap, in a complete rectangular grid. One magnet can hold all sheet corners meeting at a grid point. This clarification is additional to the printed wording; unrestricted stacking is discussed in the solution.
Clarification for the source-intended scored version: the sheets are placed edge to edge, in the same orientation, without overlap, in a complete rectangular grid. One magnet can hold all sheet corners meeting at a grid point. This clarification is additional to the printed wording; unrestricted stacking is discussed in the solution.